| Abstract | This National Standard Method (NSM) describes the identification of pathogenic Neisseria species isolated from clinical specimens and their differentiation from non-pathogenic Neisseria species and the related genera of Moraxella and Kingella. The identification of these two genera is covered in BSOPID 11 - Identification of Moraxella Species and Morphologically Similar Organisms
INTRODUCTION:
Taxonomy:
The genus Neisseria belongs to the family Neisseriaceae. The genus consists of N. gonorrhoeae and N. Meningitidis, which are of clinical significance, and several non-pathogenic species.
Characteristics of Neisseria and related organisms:
Neisseria species:
Neisseria species are obligate human pathogens with no other natural host. They are Gram-negative cocci, 0.6 - 1.0 ìm in diameter, occurring singly but more often in pairs with adjacent sides flattened. They are non-motile and flagella are absent. Some species produce a greenish-yellow caretenoid pigment and may be nutritionally fastidious and haemolytic. The optimum growth temperature is 35°C - 37°C. Neisseria are oxidase-positive and catalase-positive (except Neisseria elongata). All except Neisseria gonorrhoeae and Neisseria canis reduce nitrite.
The clinically important species of Neisseria species (Neisseria gonorrhoeae, Neisseria meningitidis, Neisseria lactamica, Neisseria cinerea and Moraxella catarrhalis) are relatively easy to identify from the non pathogenic Neisseria. N. gonorrhoeae and N. meningitidis are the two main pathogens of the group. The other species of Neisseria such as N. lactamica, N. cinerea and M. catarrhalis are generally considered commensals, but have been implicated as causes of infection in patients who are immuno-compromised.
Moraxella species:
Moraxella species may be rods or cocci. The rods are often very short and plump, resembling a
coccus shape and are usually 1.0 - 1.5 x 1.5 - 2.5 ìm in size. Cells occur in pairs and short chains with one plane of division. The cocci are smaller, 0.6 - 1.0 ìm in diameter and occur as single cells or in pairs with adjacent sides flattened. Differing planes of division sometimes result in tetrads. Cells may be capsulate. Moraxella species are Gram-negative with a tendency to resist decolourisation. Flagella are absent. Some strains may grow weakly under anaerobic conditions. Most species except Moraxella osloensis are nutritionally fastidious. The optimum growth temperature is 33°C - 35°C. Moraxella species are usually catalase-positive and no acid is produced from carbohydrates. All Moraxella species are oxidase-positive.
Kingella species:
Kingella species are straight rods, 1.0 ìm in length, often in pairs or short chains. Endospores are not formed. Cells are Gram-negative but there is a tendency to resist decolourisation. They are nonmotile. Growth is aerobic or facultatively anaerobic and the optimum growth temperature is 33°C - 37°C. Two types of colony are produced on blood agar: a spreading, corroding type with twitching motility; and a smooth convex type, which does not show twitching motility. Kingella are oxidasepositive, but may give a weak or negative reaction with tetramethyl-p-phenylenediamine. They are catalase-negative and urease-negative. Glucose and some other carbohydrates are utilised with acid production. Kingella may be mis-identified as Neisseria because they are Gram-negative rods which are often arranged in pairs, oxidase positive and may grow on GC selective agar. |